Cotton Seed Germinates on China's Moon Probe, Becomes First Off-World Plant

Update: The plant reportedly died on January 16.

New Delhi: Cotton seeds that were carried in a bucket-like tin to the far side of the Moon by a Chinese spacecraft sprouted, marking the first time that humans have grown plants in off-world conditions.

Update, January 16, 9:30 pm: The plant has died. The Guardian reported that as the temperature on the Moon’s far side dropped below -170º C, “its short life came to an end”. The scientists who had setup the experiment (details below) had apparently anticipated this outcome.

The Chinese spacecraft Chang’e 4 landed on the far side of the Moon on January 3. It carried with it a seven-inch tall bucket-like can that contained air, water, soil and seeds of potato, cotton and Arabidopsis (the mustard family) plants. On January 15, China’s state-owned television network tweeted that the cotton seeds had sprouted.

Previous experiments of growing plants in space have been limited to artificial satellites orbiting in Earth’s lower atmosphere. China has become the first country to conduct such an experiment on the lunar surface.

The Chang’e 4 spacecraft’s mission includes astronomical observations, and surveying the Moon’s terrain and mineral composition. It also plans to measure neutron radiation to help characterise the environment on the far side of the Moon.

The mission also included creating a ‘mini-biosphere’, where plants and insects could sustain each other. For this, China initially planned to carry silkworms but later decided to go with fruit flies. Scientists at Chongqing University, who are overseeing the experiment, explained that natural light will be directed to the plants through a tube inside the tin, enabling photosynthesis. They hope that the growing plants will emit oxygen, creating an ecosystem.

Also Read: China, Clearly a Country in a Hurry When It Comes to Space

The temperature, humidity and nutrition of the mini-biosphere needs to be carefully controlled to encourage the insects and plants to develop. The Moon’s temperature varies from below -100º C to over 100º C, while its surface gravity is a sixth of Earth’s. These conditions pose major challenges in sustaining the ecosystem.

According to Quartz, the team hopes to broadcast a live feed of the experiment’s progress soon.

Earlier experiments

Astronauts have successfully grown a variety of plants in our planet’s lower atmosphere, inside satellites like the International Space Station. These include leafy vegetables and flowering plants like sunflowers.

In 2013, NASA announced plans to grow plants on the Moon’s surface but it hasn’t happened thus far. The agency had said that if the plants could survive for up to 14 days, it would demonstrate that plants can sprout in the “Moon’s radiation environment at one-sixth the gravity” (of Earth).

“Survival to 60 days demonstrates that sexual reproduction (meiosis) can occur in a lunar environment. Survival to 180 days shows effects of radiation on dominant & recessive genetic traits. Afterwards, the experiment may run for months through multiple generations, increasing science return,” NASA said.

The agency has also been trying to grow plants in stimulated space environments for human spaceflight missions of the future. In these experiments, the aim will be to reduce the use of soil to grow plants, and instead use methods like hydroponics and aeroponics. While the former delivers water and nutrients to roots using liquid solutions, plants are grown in a misty air environment supported by the latter.

In 2010, researchers at the University of Arizona demonstrated a “lunar greenhouse” that could be used to grow plants on the Moon or on Mars. The greenhouse is essentially an 18-foot long tube with the necessary controls, and which will be buried underground to shield it from cosmic rays or the effects of violent solar flares.

Researchers said it will be operated autonomously. Carbon dioxide exhaled by astronauts will be fed into the enclosure through pressurised tanks, and water obtained from their urine. Sunlight could be channeled through fibre optic cables.

Also Read: How to Grow Crops on Mars If We Are to Live on the Red Planet

Using a similar approach and with NASA’s help, the university developed an inflatable, deployable greenhouse to support plants and crops for nutrition, air revitalisation and to recycle water and waste.

In May 2017, the Kennedy Space Centre’s lead scientist Ray Wheeler said the approach uses plants to “scrub carbon dioxide while providing food and oxygen”.

While the water cycle would begin with water taken from Earth, it could be recycled through oxygenation and the addition of nutrient salts.

Tests conducted at the University of Arizona included determining which plants or seeds would be suitable given the atmospheres of the Moon or Mars.